Many types of construction equipment in which a steel-made caterpillar and rubber crawler are concurrently utilized as wheels thereof have been recently made available in the market.
FIG. 1 shows one of the examples of a rubber crawler of the above mentioned concurrent type and is a cross-sectional view in the width direction thereof, showing the relationship between the rubber crawler 101 and rolling wheel 102. In addition, there is shown a middle wheel 102a, a side wheel 102b, a core bar member 103, with a projection 103a and top face m of the core bar member, respectively, a steel cord 104, and a lug 105. FIG. 2 is a side view in the circumferential direction showing the relationship with the rolling wheel as well. In FIG. 2, t is a flange or protruding part of projection 103a, and s is the interval between core bar members 103. As shown in the drawing, protruding parts t, t are provided at the front and rear parts of the projection 103a, thereby causing the core bar member 103 to be T-shaped and the top face m thereof will be a rolling track with which the side wheel 102b is brought into contact.
In the above mentioned conventional rubber crawler, the side wheel 102b of the rolling wheel 102 is brought into contact with the top face m of the projection 103a so that the base rubber material will not be damaged, thereby providing good durability thereof. However, as the rolling wheel 102 drops as a result of being between the front and rear core bar members, its running vibration increases and is made large. Therefore, in order to improve operation, the dropping or sinking of the rolling wheel is decreased by narrowing the interval s between the core bar members by making a projection 103a of the core bar member T-shaped to provide it with protruding parts. However, in this case, as shown in FIG. 2, as the protruding part t drops or sinks due to the load when the rolling wheel 2 rides on the protruding part t (the projections 103a are inclined), dropping or sinking of the rolling wheel has not been resolved. Therefore, sufficient improvement cannot be obtained for lessening the vibrations. The above description deals with the case of a mid-flanged rolling wheel.
FIG. 3 is a cross-sectional view in the width direction, showing the relationship between the rubber crawler 102' and an outer-flanged rolling wheel 102' the shape of which is different from that of the above case. In FIG. 3, there is shown an inner wheel 102'a and outer flanges 102'b of the outer-flanged rolling wheel, respectively, a core bar member 103', a projection 103'a, a stepped shoulder 103'b provided at the exterior of the projection 103'a with which the outer flanges 102'b of the outer flanged wheel are brought into contact and run thereon. The stepped shoulders 103'b are formed at a position which is at a higher level by one step than a wing portion 103'c of the core bar member 103'. There are also shown a steel cord 104' and a lug 105'.
FIG. 4 is a cross-sectional view in the circumferential direction of the rubber crawler 101' in the above embodiment. In FIG. 4, there is shown a protruding part t' of the stepped shoulder 103'b, the interval between the core bar members denoted as s', the interval between the steel cord 104' and the stepped shoulder 103'c denoted as v, a recess groove 106' provided between the core bar members.
As shown in FIG. 4, the stepped shoulder 103'b is concealed in such a manner that the top face m' thereof can be exposed out of the rubber base material of the rubber crawler 101'. As the interval s' between the core bar members and the interval v between the stepped shoulder 103'b and the steel cord 104' are made comparatively small, the ratio of compression of the interval v between the core bar members, which are compressed inwardly of the steel cords and are the turning portions for a drive sprocket wheel and an idler tumbler wheel, are made comparatively small as well. Therefore, the rolling vibration can be decreased and ensures a comparatively good feeling of riding. However, as shown in FIG. 5, when the rolling wheels are positioned between the core bar members, dropping or sinking of the protruding parts t' and t' is caused to occur due to the rolling load and vibrations still result therefrom.